MobStacker

MobStacker is a performance Minecraft mod to optimize entity handling, addressing a common cause of performance issues in vanilla and modded environments. By intelligently "stacking" similar mobs in close proximity, MobStacker significantly reduces server load and enhances client-side performance without compromising gameplay mechanics.

Requires: Dungeon Config and Fabric API. MobStacker is server side only: players don't need it installed to join.

Note: MobStacker preserves all loot and mob properties within stacked entities. Named mobs (via name tags) are exempt from stacking to maintain uniqueness.

Key Benefits

1. Server Performance Boost: Dramatically reduces entity processing overhead.
2. Enhanced Client FPS: Lowers strain on client-side rendering.
3. Optimized Network Traffic: Minimizes entity data transmission.
4. Cleaner Gameplay: Reduces visual clutter in mob-dense areas.
5. Memory Usage Reduction: Lowers overall memory footprint.

Performance Improvement

While actual performance gains vary based on server specifications, player count, and mod configurations, MobStacker can provide substantial improvements, especially in environments with:

• High mob density
• Numerous entity-adding mods
• Large, active player bases

🔗 Note:

• MobStacker has a built in configurable spawn cap module to reduce mob spawns per chunk.

Features

What Never Stacks

To keep gameplay intact, MobStacker leaves these mobs alone:

• Babies, mobs with no AI and mobs with a custom name
• Riding, ridden or leashed mobs, saddled mobs and mobs wearing body armor
• Tamed or owned mobs, horses and their relatives, and mobs released from a bucket
• Mobs carrying items, animals in love mode and player-built iron golems
• Raiders in an active raid and patrol leaders
• Villagers with a job, bed or meeting point (jobless villagers and nitwits can stack; a villager leaves its stack the moment it claims a workstation or bed, so trading halls, breeders and iron farms keep working)
• Mobs holding equipment that is guaranteed to drop
• Bosses (anything in #c:bosses or with at least bossHealthThreshold base health), unless stackBosses is on
• Anything in the #mobstacker:unstackable entity type tag, which by default includes the Ender Dragon, Wither, Warden, Elder Guardian, Wandering Trader, Allay, Bee, Vex, Happy Ghast, Copper Golem and Creaking

Configuration

The config lives at config/mobstacker/mobstacker.json5 and can also be edited in-game from the Dungeon Config screen. Old mobstacker.json configs (including mob groups and chunk overrides) are imported automatically on first launch.

Stacking

Death & Loot

Breeding

Combat

Items

Display

Filters

Mob Caps

Rules & Claims

Rules

Rules change settings for some mobs or some places, like a bigger stack size in your mob farm or no stacking at all in a boss arena. A rule can match:

• Mobs: ids like minecraft:zombie, tags like #minecraft:undead, or a whole mod like @alexsmobs (empty = every mob)
• Dimensions: like minecraft:the_nether (empty = all)
• Biomes: ids like minecraft:plains or tags like #minecraft:is_ocean (empty = all)
• Places: chunks or block areas, e.g. minecraft:overworld 0 0 63 63 (empty = everywhere)

Inside a rule every setting from the sections above (except filters for mods/entities, mob caps and the check interval) can be overridden or left on Global, and stacking itself can be switched off. When several rules match a mob, the one listed first wins. Rules are saved per world in serverconfig/mobstacker-rules.json.

With FTB Chunks (with FTB Teams) or Open Parties and Claims installed, players who aren't operators can create rules too. Their rules only apply inside chunks their team has claimed, and they can only change the settings the server allows.

Commands

All commands are prefixed with /mobstacker. Everything except /mobstacker rule requires operator permissions (level 2).

General

# Reload the config from disk
/mobstacker reload

# Show stack information for a mob
/mobstacker info [entity]

# Set stack size for specific entity
/mobstacker setStackSize [entity] [size]

Configuration Commands

# Toggle whole stack death
/mobstacker stackerConfig killWholeStackOnDeath [true|false]

# Toggle health stacking
/mobstacker stackerConfig stackHealth [true|false]

# Set maximum stack size
/mobstacker stackerConfig maxStackSize [value]

# Set stack radius
/mobstacker stackerConfig stackRadius [value]

# Set how often mobs look for a stack (ticks)
/mobstacker stackerConfig stackCheckInterval [value]

# Toggle stack melee damage multiplier
/mobstacker stackerConfig stackOutgoingDamage [true|false]

# Set how many mobs die per kill
/mobstacker stackerConfig killBatchSize [value]

# Set batch breeding size and cooldown
/mobstacker stackerConfig breedBatchSize [value]
/mobstacker stackerConfig breedCooldown [value]

# Toggle tool and weapon wear scaling
/mobstacker stackerConfig scaleToolDamage [true|false]
/mobstacker stackerConfig damageWeaponPerHit [true|false]

# Toggle villager stacking
/mobstacker stackerConfig stackVillagers [true|false]

# Toggle separator functionality
/mobstacker stackerConfig separator enableSeparator [true|false]

# Toggle separator consumption
/mobstacker stackerConfig separator consumeSeparator [true|false]

# Set separator item
/mobstacker stackerConfig separator separatorItem [item_id]

# Toggle assimilator functionality
/mobstacker stackerConfig assimilator enableAssimilator [true|false]

# Toggle assimilator consumption
/mobstacker stackerConfig assimilator consumeAssimilator [true|false]

# Set assimilator item
/mobstacker stackerConfig assimilator assimilatorItem [item_id]

Entity and Mod Management

# Ignore specific entity
/mobstacker ignore entity [entity_id]

# Ignore all entities from a mod
/mobstacker ignore mod [mod_id]

# Remove entity from ignore list
/mobstacker unignore entity [entity_id]

# Remove mod from ignore list
/mobstacker unignore mod [mod_id]

NOTE: An entity can be given the tag {StackData: {CanStack:0b}} to prevent it from stacking. Entity types can also be added to the #mobstacker:unstackable tag with a datapack.

Mob Cap Management

# Toggle mob cap overrides
/mobstacker mobCapConfig enableMobCapOverrides [true|false]

# Set the cap for a mob category
/mobstacker mobCapConfig monsterMobCap [value]
/mobstacker mobCapConfig creatureMobCap [value]
/mobstacker mobCapConfig ambientMobCap [value]
/mobstacker mobCapConfig axolotlsMobCap [value]
/mobstacker mobCapConfig undergroundWaterCreatureMobCap [value]
/mobstacker mobCapConfig waterCreatureMobCap [value]
/mobstacker mobCapConfig waterAmbientMobCap [value]

Rule Management

Rule pages in chat are clickable, so most of this can be done without typing the full commands.

# List rules (or just /mobstacker rule)
/mobstacker rule list

# Create or delete a rule
/mobstacker rule add [name]
/mobstacker rule remove [rule]

# Open a rule's page
/mobstacker rule [rule]

# Turn a rule on or off
/mobstacker rule [rule] enable
/mobstacker rule [rule] disable

# Change which rule wins when several match (operators only)
/mobstacker rule [rule] priority [position]

# Edit which mobs, dimensions and biomes a rule covers
/mobstacker rule [rule] mob [add|remove] [mob_id|#tag|@mod_id]
/mobstacker rule [rule] mob clear
/mobstacker rule [rule] dimension [add|remove] [dimension_id]
/mobstacker rule [rule] dimension here
/mobstacker rule [rule] biome [add|remove] [biome_id|#tag]
/mobstacker rule [rule] biome here

# Add places to a rule
/mobstacker rule [rule] place chunk [chunkX] [chunkZ]
/mobstacker rule [rule] place chunks [radius]
/mobstacker rule [rule] place area [x1] [z1] [x2] [z2]
/mobstacker rule [rule] place remove [number]
/mobstacker rule [rule] place clear

# View and change a rule's settings
/mobstacker rule [rule] settings [page]
/mobstacker rule [rule] set [setting] [value]
/mobstacker rule [rule] reset [setting]

API

Other mods can integrate through MobStackerAPI:

• getStackSize(mob): how many mobs a mob stands for
• addMergingCondition(...): extra conditions two mobs must meet to merge
• addDeathHandler(...): runs when a stacked mob dies and the rest of the stack takes its place
• addEntityDataModifiers(...): adjust the mob that replaces a dead or exploded stacked mob
• addEntityDataModifiersOnSeparation(...): adjust a mob split off with the separator
• registerClaimProvider(...): add support for another land claim mod

Additional Notes

• Mobs periodically look for a nearby stack to join (every stackCheckInterval ticks).
• When a stacked creeper explodes or an enderman picks up a block, only that one mob does it; the rest of the stack stays behind.
• Stacked mobs display stack size in their name (e.g., "Zombie x5"), shown in each player's own language.
• Compatible with various entity types: animals, monsters, and NPCs.

Report issues to the issue tracker on github.